Effects of protein level in isocaloric diets on growth performance of the juvenile Chinese hairy crab, Eriocheir sinensis

Abstract

A feeding trial was conducted in a semi-recirculating water system to investigate the effects of the dietary protein level in isocaloric diets on growth performance of juvenile Chinese hairy crabs, Eriocheir sinensis. Six shrimp meal based diets, which contained various protein levels (29.8 to 54.8%) with the digestible energy of 3.47 to 3.55 kcal/g dry matter, were formulated and fed to crabs for 35 days. The diet containing 39.0% dietary protein produced the best values in weight gain (WG), specific growth rate of body weight (SGRw), feed conversion (FC), protein efficiency ratio (PER) and body protein gain (BPG). Crabs fed the 39.0% protein diet had significantly higher WG than those fed the 29.8 and 34.1% protein diets. There were no significant differences in WG, SGRw, FC, PER and BPG values among crabs fed the 44.2, 48.7 and 54.8% protein diets. The PER and apparent protein utilization (APU) of crabs fed diets with 29.8, 34.1 and 39.0% dietary protein were significantly higher than those of crabs fed higher dietary protein. The protein level for maximal growth was estimated to be 42.5%. Body protein content was not significantly affected by the dietary protein level. The contents of body lipid and carbohydrate tended to decrease as the dietary protein level increased. These results indicate that the optimum dietary protein level ranges from 39.0 to 42.5% for juvenile E. sinensis.